In article , Graham J wrote:
I don't see that as being too difficult, provided you don't
try to be too clever about it and try too hard to limit it to
genuine bus-tube or tube-bus through journeys. Just make it a
general case that any tube ticket bought within a certain time
of any bus ticket attracts a discount, and vice versa, where
that time could be extremely generous (say a couple of hours).

That's the system they have in Melbourne: "Two Hour Metcards allow
unlimited train, tram and bus travel for at least two hours within
selected zones on the day of first validation.

The ticket expires two hours from the next full hour after the
first validation. For example - a ticket validated at 9.05 am will
expire at 12.00 noon and a ticket validated at 8.55 am will expire
at 11.00 am.

In addition, tickets first validated after 6.00 pm are valid until
the end of services for that day."

http://www.metlinkmelbourne.com.au/m...es/twohour.php

2 hours is A$3.10 v. A$5.90 for a one-day pass (Zone 1, say 10 mile
radius of city centre) = £1.25/£2.40 approx.

--
Tony Bryer